These are some of the options being seriously considered in efforts to restrain human-induced climate change.

An understanding of the scientific knowledge indicates that attempts at returning the climate to anywhere near its original condition will require an effective planetary defence effort on the scale spent on the military — which has totalled more than $20 trillion since World War II.

This kind of action is not presently occurring. Atmospheric carbon dioxide is triggering amplifying feedbacks, and therefore efforts at reduction in atmospheric CO2 emissions are no longer sufficient to prevent further global warming. Efforts need to be undertaken in an attempt to reduce atmospheric CO2 levels from their current level of near 400 parts per million (ppm) to well below 350 ppm.

The scale and rate of modern climate change have been greatly underestimated. The release of a total of over 560 billion tonnes of carbon through emissions from industrial and transport sources, land clearing and fires, has raised CO2 levels from about 280 ppm in pre-industrial periods to 397-400 ppm, reaching a current CO2 growth rate of about 2 ppm per year.

The current CO2 level generates amplifying feedbacks, including the reduced capacity of warming water to absorb CO2 from the atmosphere, released from fires, droughts, loss of vegetation cover, disintegration of methane released from bogs, permafrost and methane-bearing ice particles and methane-water molecules.

With CO2 atmospheric residence times in the order of hundreds to tens of thousands of years, protracted reduction in emissions, either flowing from human decision or due to reduced economic activity in an environmentally stressed world, may no longer be sufficient to arrest the feedbacks.

Four of the large mass extinction of species events in the history of Earth have been associated with rapid perturbations of the carbon, oxygen and sulphur cycles, on which the biosphere depends, at rates to which species could not adapt.

Since the 18th century, and in particular since about 1975, the Earth system has been shifting away from Holocene (from approximately 10,000 years ago) conditions, which allowed agriculture, previously hindered by instabilities in the climate and by extreme weather events. The shift is most clearly manifested by the loss of polar ice. Sea level rises have been accelerating, with a total of more than 20cm since 1880 and about 6cm since 1990.

For temperature rise of 2.3 degrees, to which the climate is committed if sulphur aerosol emission discontinues, sea levels would reach Pliocene-like levels of 25 metres plus or minus 12 metres, with lag effects due to ice sheet inertia.

With global atmospheric CO2 equivalent (a value which includes the effect of methane) above 470 ppm, just under the upper stability limit of the Antarctic ice sheet, with current rate of CO2 emissions from fossil fuel combustion, cement production, land clearing and fires of about 9.7 billion tonnes of carbon in 2010, global civilisation faces the following alternatives:

With carbon reserves sufficient to raise atmospheric CO2 levels to above 1000 ppm, continuing business-as-usual emissions can only result in advanced melting of the polar ice sheets, a corresponding rise of sea levels on the scale of meters to tens of meters, on a time scale of decades to centuries, and high to extreme continental temperatures rendering agriculture and human habitat over large regions unlikely.

With atmospheric CO2 at about 400 ppm, abrupt decrease in carbon emissions may no longer be sufficient to prevent current feedbacks (melting of ice, methane release from permafrost, fires). Attempts to stabilise the climate require global efforts using a range of methods, including global reforestation, extensive biochar application, chemical CO2 sequestration (using sodium hydroxide, serpentine and new innovations) as well as burial of CO2.

As indicated in Table 1, the use of short-term solar radiation shields such as sulphur aerosols cannot be regarded as more than a band aid, with severe deleterious consequences in terms of ocean acidification and retardation of the monsoon and of precipitation over large parts of the Earth. By contrast, retardation of solar radiation through space sunshade technology, may allow time for CO2 draw-down. Unlike sulphur dioxide injections this will not have ocean acidification effects — an effort requiring a planetary defence project by NASA.

Dissemination of ocean iron filings aimed at increasing fertilisation by plankton and algal blooms, or temperature exchange through vertical ocean pipe systems, are unlikely to constitute effective means of transporting CO2 to storage at relatively safe water depths.

By contrast to these methods, CO2 sequestration through fast track reforestation, soil carbon, biochar and possible chemical methods such as “sodium trees” may be effective, provided these are applied on a global scale.

It is likely that a species which decoded the basic laws of nature, split the atom, placed a man on the moon and ventured into outer space should also be able to develop the methodology for fast sequestration of atmospheric CO2. The alternative, in terms of global heating, sea level rise, extreme weather events, and the destruction of the world’s food sources is unthinkable.

*Andrew Glikson is honorary professor in earth and paleoclimate science at the University of Queensland, and visiting fellow at the Australian National University

Hugh McColl, are you saying that we must dirty our dishes in order to eat and thus must clean up after ourselves?

One difference to your metaphor is that we don’t need to emit carbon to get energy. To be sure, we need a emergency-type effort to create massive energy storage technology. Already, we should be mass producing (N-word) power stations, for the entire world.

The other difference is that the means to clean away our waste gases are hopelessly inadequate. Consider that every year, 40 gigatons, that’s twenty thousand cubic kilometres, of CO2 should be permanently buried in some place where carbon would not otherwise appear. It can’t be done. Toying with these silly schemes offers us an illusion of innocence, but will not fool any jury of survivors.

One might quibble with some of the statements here. For example “sodium trees” seem a highly unlikely solution for at least two reasons which are the same as for Carbon Capture and Sequestration for coal-fired power stations (essential identical technology): 1. energy cost and 2. sequestration of CO2. The iron-seeding of oceans is, IMO, much more promising than almost any other technology, as Crikey readers should know from my article:

(crikey.com.au/2010/06/11/geoengineering-does-not-remove-the-need-to-decarbonise/)
Friday, 11 June 2010 /
Geoengineering does not remove the need to decarbonise
by Michael R James

Bio-sequestration has enormous potential in the form of iron seeding of oceans and charcoal in soils. But again a lot of research is required as no one really understands the processes or long-term effects. There is some optimism for ocean seeding because it is potentially easy, cheap and scalable — and innocuous. There are vast segments of the Pacific ocean that are dead zones with very little life — because they are a long way from coasts and do not have currents to bring nutrients, one of which, iron is limiting to the growth of blue-green algae and phytoplankton, the very bottom of the whole ocean food chain.
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This is kind of equivalent to carbon capture and storage (CCS) except it is done naturally by organisms and the carbon is sequestered as stable calcium carbonate skeletons that fall to the ocean floor at the end of the animals’ life. In fact it is a kind of solar power as the energy that drives the process is free from the sun coupled to a billion years of biological evolution. It is why it is economically feasible and clean coal is not. This process is the origin of the massive limestone deposits throughout the world, such as those exposed in the White Cliffs of Dover. Staggering amounts of carbon are embedded in these deposits and in principle, creating some more in some unoccupied part of the Pacific may well be ecologically innocuous and very affordable.

But one cannot quibble with the need for serious research on any or all of these potential methods. Some may play a short-term role, eg. increasing the upper atmosphere’s albedo via various methods including sulphur, reflective microparticles (that stay aloft a lot longer) and water vapour. Others such as ocean seeding may be a longer term method of permanently sequestering carbon; any pessimism needs to acknowledge that it has happened — those white cliffs of Dover and all limestone and marble deposits etc. The research needs to be done to find optimal conditions, and yes, if the sequestration can be made permanent (the acidification of oceans is what can cause calcium carbonate to re-dissolve but deep ocean — especially in the precise areas of the Pacific likely to be used for any ocean seeding — is surely the last to be acidified (it requiring exchange with surface water which by definition is what doesn’t happen in these areas).

Even Clive Hamilton has changed his mind on the importance of this research as he revealed on a recent ABC Lateline; see my earlier article which was in part a response to Hamilton’s antipathy to any kind of geo-engineering at that time.

I too have always thought using sulphur injection into the upper atmosphere to be an odd approach, however the amount needed is presumably a lot less than the amounts our old dirty coal-burning put into the air that caused acid-rain.

In any case as a biochemist, naturally I prefer the bio-sequestration approach discussed in my post above. As to Dr Glikson’s closing words: “By contrast to these methods, CO2 sequestration through fast track reforestation, soil carbon, biochar and possible chemical methods such as “sodium trees” may be effective, provided these are applied on a global scale.” I cannot imagine the land-based methods having the chance of a snowflake in hell as they are in such conflict with developmental aims of the parts of the planet where they would have to happen. Worse, at any time and in short time frames, all the good work could be undone by political action/inaction. if it works, ocean-seeding sequestration would not be subject to such political problems.

I too have always thought using sulphur injection into the upper atmosphere to be an odd approach, however the amount needed is presumably a lot less than the amounts our old dirty coal-burning put into the air that caused acid-rain.

In any case as a biochemist, naturally I prefer the bio-sequestration approach discussed in my post above. As to Dr Glikson’s closing words:

“By contrast to these methods, CO2 sequestration through fast track reforestation, soil carbon, biochar and possible chemical methods such as “sodium trees” may be effective, provided these are applied on a global scale.”

I cannot imagine the land-based methods having the chance of a snowflake in h*ll as they are in such conflict with developmental aims of the parts of the planet where they would have to happen. Worse, at any time and in short time frames, all the good work could be undone by political action/inaction. if it works, ocean-seeding sequestration would not be subject to such political problems.

Deposition of calcium carbonate from seawater does remove CO2, however it increases acidity because the calcium ion has been replaced by hydrogen ions. Accumulating acidity can only be replaced by cations from the slow geological process of weathering of rock. If 280 ppm CO2 is indeed an equilibrium of some sort, it would only be reached again long after our (carbon belching) species has vanished from the face of the earth.

Perhaps it is our extinction which is unthinkable, as unthinkingly we destabilise the environment that evolved us. Vandalism is indeed a good word for it, but the scale of destruction seems to be beyond our conception.

If people can’t be bothered listening to some like Andrew who offers a whole range of responses - then we really are doomed.

The real irony of what Andrews writes is that in shorthand it would be called Direct Action. Which will always remain the only way to actually do something.

Sin Taxes on carbon will never work. James Hansen clearly says in his essays the past year and massive tree planting and soil sequestration are the only possible ways to get the CO2 level down from 400ppm to 350ppm.

The AGW science leadership is pointing the way to solutions - time to listen to not just the science of global warming but the solutions these same scientists are pointing to.

The New Scientist article “Marine Snow”, contrary to claims in the article, does provide evidence that carbon sequestered in the dead bodies of zooplankton and phytoplankton will, indeed, sink to the bottom of the ocean just as, the title suggests, snow falls to the ground.
Another example of experts being , in fact, ignoramuses.
Most of the world’s biological carbon is found, sequestered, on the ocean floors.
Ask any high school geology student, it is in their text books. It is just too hard, isn’t it, picking up a book; are you all suffering from the “Abbott Syndrome”?
Lazy and arrogants c-nts?
All looking forward to the life eternal?
Gaiaologists all servants of the devil, out to doom their victims to hell?
Pick up a book you clowns!

I’m really starting to like you Hamis. You offer some real competition in calling a spade a spade and smacking them right back. Keep up the great work and I promise to read my Adam Smith in detail this xmas. It’s just such heavy going - you can only read one chapter a month before your head gets warped in the old English prose.

Yes, Simon, ten or so pages per article, taken from his lectures perhaps, and I end up slackjawed at the profundity of the arguments.
Definitely a no ifs or buts communicator, and too rich to consume the whole work in one go.
But a definite anti-dote for the drivel of modern specialists.

Roger, I think you are a bit confused about that. It is the dissolution of CO2 in water to create bicarbonate that creates the acidity. The generation of calcium carbonate (by organisms) ultimately results in reduced acidity because it reduces the total CO2 (as carbonate).

H20 + 2 xCO2 → 2x(HCO3)2- (carbonate ion)

Ca2+ + 2HCO3 2- → CaCO3 (limestone) + CO2 + H2O

(Overall the reaction takes one molecule of CO2 out of the water. In seawater the liberated CO2 immediately forms carbonate; ie. the equivalent of 2 molecules of CO2 are input and one is ouput)

Many people can test this at home: use a SodaStream to heavily carbonate (with compressed CO2 gas) some cold water and it will become acid — which one can tell even without pH litmus paper because it tastes acid. Warm it up and shake the heck out of bottle and most will be liberated back into the atmosphere and the water will lose most of the acidity. Of course the same is true for a bottle of your fave cola — the most acid of carbonated drinks — which is largely why it tastes so “awful” when warm and flat (degassed).

I too have always thought using sulphur injection into the upper atmosphere to be an odd approach, however the amount needed is presumably a lot less than the amounts our old dirty coal-burning put into the air that caused acid-rain.

In any case as a biochemist, naturally I prefer the bio-sequestration approach discussed in my post above

A number of posts have suggested that limiting emissions is more desirable than the geoengineering solutions discussed in the article. No one disagrees with that, and it’s not presented by the author as an alternative.. The article is considering what steps might be necessary to return the Earth to, say, 300 ppm. Because of amplifying feedback, that will take more than limiting emissions.

If humans only learn about comparitive cost from experience, then we are truly fucqed.

Trenberth’s 0.9W/M2 warming imbalance has now been reduced by Hansen to about 0.6W/M2 because of Chinese aerosol emissions according to Hansen. The missing heat in the Oceans is still missing. Trenberth does not agree with Hansen’s reduction ‘for a minute’.

Recent evidence points to a warming imbalance of 0.2-0.4W/M2 from OHC measurement.

The TSI has been assumed at 1366W/M2 in all incoming solar calculations until recently. An outlier measurement by SORCE TIMS satellites of 1361.5W/M2 since 2005, was poo-pooed by Trenberth and co until last December AGU meeting when a French group confirmed the 1361 number. Gavin Schmidt confirms that the 1361 number is right and will work its way through the literature.

Trouble is that this number blows Trenberth’s warming imbalance calculation out of the water and points to an imbalance closer to 0.3W/M2 than 0.9W/M2.

So with logrithmically rising CO2GHG radiative forcing with rising CO2 in the atmosphere - there is a large DECREASE in the measured and theorized warming imbalance - a result which defies AGW predictions.

Glikson should know these facts yet continues with his alarmist nonsense about 25m sea level rises and giant umbrellas.

It seems to me the solution is simple.
Get all the climate scientists to have a conference in Washington. Pack all the available nuclear weapons in the subways beneath Washington. At midday detonate them.

The resulting explosion should push the earth out to an orbit further away from the sun. All the climate scientists won’t be around to annoy us anymore and there will be an outbreak of world peace.

If we found we have overcompensated we could always then detonate all Israel’s nukes at midnight, that would send us back inwards a little and provide yet further gains in world peace

I really, truely like this article. It says that which must be said without pulling punches.

The future of our species and many others depends on us making the correct decisions right here and right now. Ancient shibboleths must be challenged. These include using any and all carbon-free energy sources in preference to (say) fossil fuels, even those which happen to be less fierce than some others. Gas is not better than coal. It is less worse.

As someone said upthread, nuclear power must be in the lineup alongside solar, geothermal and wind.

Many thanks, Andrew. It’s refreshing to see someone with skin in the game say it like it is, bluntly and with passion.

Arctic sea ice is shrinking on an annualized basis - Antarctic sea ice is growing. Overall there is a small loss. Insignificant in energy terms compared with the claimed global warming imbalance which is what really count.

It reveals the SORCE TSI of 1361.5 W/M2 as being confirmed at AGU December 2011 meeting. It also reveals the Trenberth-Hansen disagreement over warming imbalance and the Skeptical Science comments by Trenberth previously unknown to Gavin Schmidt. It ends in silence from Schmidt on the warming imbalance.

Some of the Arctic warming was predicted to be as a result of Russion Arctic rivers being diverted for irrigation.
The fresh water formerly floated on the salty water and being less dense also more easily froze, reflecting heat back into space (albido).
Salty water, deprived of this cover of easily frozen fresh water in the Arctic ocean, absorbed and stored more heat and remaining unfrozen for longer absorbed even more heat fron the sun.
So now you know, anthropogenic global warming is real, it is all a communist plot and the Gillard Labor government is at the heart of it!!!
They have broken the covenant, just ask Tony.

Dillard, Swandive and Wongskies told me that all would be made right in the world with the Carbon Tax and jacking up my electricity bills.

What are you saying, that I’m paying for the Carbon Tax and nothing is actually fixed?

Sounds like what we need is a direct action plan that makes new renewable technology science a reality not a great big new tax. Oh wait.. thats the Coalitions plan. Quick Greenies.. time to eat that humble pie.

Deposition of calcium carbonate does indeed increase the acidity of the oceans. In my comment above, I was implying that there is a net reaction: Ca++ + CO2 + H2O -> CaCO3 + 2H+ — the reverse of “neutralisation” that we learnt in school.

Of course you would be correct in saying that is simplistic, that there is a chain of equilibria between the different carbon species in seawater (solvated CO2, H2C03, HCO3-, CO3 — ), however the net effect is the same, removal of CO3 — at one end results in an increase of two H+ at the other. In fact, if you balance your own equations, you will see the production of H+ there.

The recovering process, neutralisation, occurs when cations are released from rocks during weathering. But that process is geological, much slower than 40 gigatons of CO2 per year.

So answer me this, concerning tha ice imbalance between the Arctic and Antarctic, in the past Ice Ages where did all the ice come from?
Was it previously in the atmosphere as a result of warming seas?
Isn’t Antarctica, and not Australia, the driest continent on Earth?
So where is all this extra ice coming from?
Global warming?
Complicated?

Tx for reply. I’m still trying to get my head around it.
I cannot find (Wiki etc) a complete accounting of the whole cycle.

As I understand it, the massive deposits of various forms of calcium carbonate around the world — such as those white cliffs of Dover which are old ocean beds compressed and uplifted to form most of what today is most of SE England & NW France — were formed in the carboniferous era. ie. the water-based equivalent of land-based massive growth of forests etc which led to organic deposits that turned into coal, oil and gas over geological time. The carboniferous was the “response” (one could turn all Gaia here) to the massive gasification of the atmosphere via the last major burst of planet-wide volcanic activity.

If formation of calcium carbonate causes acidification what stopped the oceans becoming totally toxic in acidity. Indeed the deposition of the CaCO3 should never have happened since below a certain pH it re-dissolves? Something seems missing from this scenario.

Deposition of calcium carbonate is a process in equilibrium with the alkalinity of the sea.

Corals form on the shallow edges of the oceans and may be subducted as reefs. Serpentinisation of the mid-ocean basalts supplies cations and alkalinity. The rate of formation of coral and serpentinite depends on the alkalinity of the sea and vice versa, with the balance near pH 7.8. Rivers supply cations and bicarbonate, but are more acid than the sea. Otherwise carbon dioxide that enters the oceans eventually returns to the atmosphere. The term “ocean overturn” occasionally occurs in the literature to explain sudden global warming events in the ice cores.

Including the chalk of the White Cliffs of Dover, limestones of sedimentary basins were laid down in relatively shallow seas continuously supplied with sediment from higher ground. About 10% of the sedimentary layers were laid down down as biogenic calcite (CaCO3) in relatively alkaline water, but most of the time laid down silica as sand and silt under an atmosphere too acid for calcite.

It is true that the broad ocean is depleted in iron (and in some places silica) as a result of biomass sinking below the mixing layer — an oxygenated and warmed layer, usually about 100 m deep, stirred by waves from the surface. Delicately termed “organic detritus”, the faecal matter is converted to tiny bacterial slimes of very low sink rate, perhaps another hundred metres deeper. Storms occasionally raise waves that reach into this carbon-rich layer and return some of it to the surface.

Waves also travel horizontally along the interface and may breach the surface to release CO2 and minerals there. The most famous such breaching occurs off the coast of Peru where the emerging fertiliser gives rise to an anchovy industry. Often around Christmas (that’s El Niño in Spanish) the warmer mixing layer covers over the rich water and suppresses the anchovies.

The bacterial slimes slowly aggregate and eventually reach flocs of a centimetre or so in size that begin to descend into the various middle layers of the ocean, to surface as CO2 somewhere else on timescales of a few hundred years — too soon to be called “sequestration”. A small proportion of the slimes reaches the abyssal depths (1 to 3 km) where it provides food for the bottom dwellers and leaves a fine layer of calcareous (CaCO3) ooze. As the ocean crust slides downhill past 3 km, increased water pressure redissolves the ooze.

In addition to your points of clarification, Ron, the ice which must have formed from precipitation on the now dry continent of Antarctica, (as opposed to the sea ice you have dealt with)where did it come from if not higher humidity, higher temperatues and more powerful storms.
All indications of warming.
Once transported thus to the poles then this water has to freeze in winter and build up hundreds of metres deep.
So hot tropics lead to more precipitation at the poles?
There has to be a mechanism for the building up of the land based ice sheets which involves precipitation which has not been happening now in the interglacial period.

I’m not nitpicking just to be argumentative, but I still fail to really understand, possibly because it is over geological timescales. Here are some points that baffle me.

-Rivers supply cations and bicarbonate, but are more acid than the sea.
-About 10% of the sedimentary layers were laid down down as biogenic calcite (CaCO3) in relatively alkaline water …
-slimes reaches the abyssal depths (1 to 3 km) where it provides food for the bottom dwellers and leaves a fine layer of calcareous (CaCO3) ooze.
-As the ocean crust slides downhill past 3 km, increased water pressure redissolves the ooze.

So the first few points still leaves obscure the source of the alkalinity — if it cannot be from rivers. But is the main factor a slight tipping towards alkaline seas in certain (rare?) geo-marine environments that allows a (transient — millions of years) deposition of CaCO3? Are there areas today that are still doing this? (Regardless of the long timescales I still see the huge amounts of such depositions — eg. untold trillions of tons underlying England and English channel & North Sea — as needing a huge source of alkalinity to work?)
Also, I understood limestone deposits like those chalk cliffs were 100% biological in original and not sure if you are saying only 10% of it is, mixed in with inorganically-formed calcite?; or if only 10% of such geo-formations around the world are of bio-origins?
Does increasing pressure redissolve CaCO3? (Yikes, I must have an appalling blackhole in my knowledge: I can see that pH and temperature change with depth, and that these are powerful conditions (that should mostly stabilize such deposits?) but for the life of me I cannot see why high pressure would do anything other compress it all into “rock”. Of course high pressure with high temperature is a different matter — that is the kind of process producing marble etc from other forms of CaCO3. )

Does increasing pressure redissolve CaCO3?
Yikes, I must have an appalling blackhole in my knowledge: I can see that pH and temperature change with depth, and that these are powerful conditions (that should mostly stabilize such deposits?) but for the life of me I cannot see why high pressure would do anything other compress it all into “rock”. Of course high pressure with high temperature is a different matter — that is the kind of process producing marble etc from other forms of CaCO3.

~Rivers supply cations and bicarbonate, but are more acid than the sea.
~About 10% of the sedimentary layers were laid down down as biogenic calcite (CaCO3) in relatively alkaline water …

So the first few points still leaves obscure the source of the alkalinity — if it cannot be from rivers. But is the main factor a slight tipping towards alkaline seas in certain (rare?) marine environments that allows a (transient — millions of years) deposition of CaCO3? Are there areas today that are still doing this? (Regardless of the long timescales I still see the huge amounts of such depositions — eg. untold trill ions of tons underl ying England and English channel & North Sea — as needing a huge source of alkalinity to work?)

Also, I understood limestone deposits like those chalk cliffs were 100% biological in original and not sure if you are saying only 10% of it is, mixed in with inorganically-formed calcite?; or if only 10% of such geo-formations around the world are of bio-origins?

Check out “carbonate compensation depth”, below which calcite redissolves. In equilibrium with the preindustrial atmosphere of CO2 ~ 280 ppm, it has been between 3 and 6 km deep in the oceans, but is now shallowing as the downwelling water becomes increasingly acidic.

Where does the alkalinity come from to allow the great limestone beds to form?

Limestone beds form in sedimentary basins (shallow seas), not the open ocean. Rock in high ground surrounding a shallow sea gets weathered (hydrolysed) and washed into the basin. Rock minerals are typically compounds of strong basic oxides and weak acidic oxides. Mostly the weak acidic oxide is SiO2, and the most common of the strong basic oxides is MgO, followed by K2O, CaO and others. Consequently, the groundwaters carrying away the weathering products are alkaline. (Inland salt lakes in Australia are typically alkaline, where their calcite deposits convert to gypsum beds.)

Surface waters do absorb CO2 from the air so that rivers which actually reach the ocean have pH values typically below 7.5. However shallow inland seas can lose CO2 again, for example as the temperature rises under a hot sun. Although animals are producing calcite shells all the time, the rate at which the shell deposits redissolve varies with the ancient climates. About 10% of sedimentary beds are carbonates that have survived redissolution, providing a record of the ancient climates as well as the species that laid them down.

@ Michael R James: your questions sent me to check my facts, and I have indeed made an error. Groundwater attacks parent rock because it is (and remains) acidic, both from incoming CO2 and from oxidation of sulphides in the rock. Alumina released from the rock forms typically kaolin (and kin), which buffers the water to pH 4.2. Less commonly it forms clays with higher silica, buffering the water up to pH 5.5. Those values are my own measurements from the clays around Perth (WAust), so the figures may be revised.

Further, I have neglected a key process in shallow basins — evaporation. If the basin has limited access to the open ocean, evaporation will remove H2O and CO2. That is, it is evaporation that makes the lake water alkaline. The reducing water becomes saturated in salts such as sodium chloride and calcium carbonate, which deposit in turn. While the water is saturated with respect to calcium carbonate, shell beds accumulate.

Would this process remove waste CO2 from the atmosphere faster than industrial man replaces it? Well, it would have to be removing more than ~40 g/m2/a CO2 from the greenhouse. If purposely-dammed basins were to have an area of say 1% of the Earth’s surface, they would have to deposit calcite at more than 4 kg/m2/a, which I doubt is practicable. And I for one would defend that 1% from such vandalism!

It has beeen shown that metal meshes in shallow water, when electified by a direct current cause deposits of calcite and other carbonates to form on the mesh.
One proponent of this technology proposed to fabricate calcareous structures resemblind reinforced concrete fro infrastructure uses.
Vandalism or a contribution to reducing global warming?